1. Field of the Invention
The present invention relates to a self-locking nut for fastening an eye-glass lens to a frame or the like, to a nut tightener for tightening or loosening a small nut used in eye glasses, and to a nut supplier which enables efficient assembling and repairing of eye glasses using small-sized plastic nuts.
2. Description of the Prior Art
In general, lenses of rimless-type eye glasses are fastened to metal members or the like through the following procedure shown in FIG. 1: first, a pair of T-washers 31 are fitted into a hole 22 formed in a lens 21 from both ends; and then the lens 21 is attached to a metal member 24 by means of a small screw 25 and a nut 32. However, since the simple tightening of the normal metal nut cannot substantially provide a self-locking effect, the loosening of the nut will occur during a long period of use. To prevent this, it is possible to use a double nut and slightly rotate its inner element in the reverse direction at the final stage of tightening so as to prevent the fastening device from loosening, due to the combined effect of both elements of the double nut. In the case of using the double nut, however, a male screw with a long shank should be used. Moreover, since the double nut consists of two elements, the fastening device becomes heavier accordingly, resulting in the overall imbalance and impaired appearance of eye glasses. Hence, the use of a double nut is not preferred for eye glasses in which light weight and good appearance are valuable factors.
Furthermore, since it is necessary in rimless-type eye glasses to fit the T-washers 31 into the hole 22 in the lens from both ends in order to prevent the breakage of the lens at the time of fastening the screw as described above, a larger number of parts are used to assemble eye glasses, which results in reduced assembling efficiency and increased production cost. In view of the foregoing, there has conventionally been a demand for a nut for eye glasses which realizes improved assembling efficiency without increasing production cost.
In addition, since a small nut for eye glasses is hard to handle with fingers, it is difficult for a worker to properly guide the nut to an intended position in a material to be fastened prior to the fastening operation. Consequently, the fastening operation requires much attention and labor from the worker, and there is a possibility that the worker drops the nut onto the lens surface by mistake, thereby damaging the lens. Hence, a small nut which can easily be handled and set to an intended position in eye glasses has been awaited.
The conventional metal nut is also disadvantageous in that its appearance may be impaired by the generation of corrosion and that the nut may be unfastened due to the development of corrosion during a long period of use, which may cause the falling of the lens or other trouble. To prevent such trouble, a method of covering the fastened nut with a plastic cap, separately produced, has been adopted for moisture prevention. However, the method of attaching the water-proof plastic cap requires an additional step of attaching the moisture-proof cap as well as a larger number of parts to assemble eye glasses. Consequently, the efficiency with which eye glasses are assembled is reduced, while production cost is further increased. Hence, there has conventionally been a demand for a water-proof nut for eye glasses which is low in cost and improves assembling efficiency.
However, since the nut used in eye glasses is extremely small as described above, there is a case where the worker tightening the nut mishandles a spanner away from the intended position onto the lens surface or where the worker drops the spanner onto the eye glasses by mistake. Conventionally, a metal spanner has been used for tightening the eye-glass nut to be attached. However, the metal spanner is comparatively expensive, and if mishandled, it may cause a serious damage to the main body or lens of the eye glasses. Since it is difficult to handle and rotate the small nut used in eye glasses with fingers and it requires considerable attention and labor from the worker engaged in the tightening operation, the conventional spanner for eye glasses is not perfect as a tool for tightening such a small nut securely and easily. Moreover, the screw fastened to eye glasses may loosen anywhere at any time. If the screw is left loosened, the lens may fall out of the eye-glass frame or other trouble may occur, so that the screw should be retightened every time it loosens. However, since the conventional metal spanner is heavy in weight and may cause a damage to the lens if mishandled, it is not suitable for use as a nut tightener to be constantly carried and used, if necessary, by a common eye-glass user. Consequently, a nut tightener for eye glasses which enables easy and secure tightening of the small nut has conventionally been awaited.